First, a lot more "old" denominations - Catholic, Lutheran, etc.
Second, you read Dawkins (I believe) He talks about the free market system in the US. Many European countries have a State or at least Dominate religion (Church of England, Catholic Church). There is no competition. A competative, open capitalist market forces innovation.
I mean, does your cable service ever really get better, cheaper? No, because there is only one cable company in town. But look at Electronics - new iMP3 players, tvs, computers, software, satelite radios, etc are coming out each month. They always need to build a better mousetrap to get the customers.
In America, there is so much choice in churches. I live in the city, I can walk to 22 churches in a 10min / 3/4 mile radius, including 3 Catholic parishes. Churches need to be sexier, sleeker, more targeted to meet the audiences to attract new "customers". We are a consumer culter that likes our products tailored to or individually and personality. We want to be catered to. Churches know this. So they preach the Gospels in a way that their local want to hear, they have Church groups that appeal to the congregation to build a bigger community.
I wont ramble any further, but Dawkins and others explain it better.